This invention relates to a swivel-mounted pneumatic-controlled releasing hook device for lifting packages and other cargo.
Heavy packages are lifted by a group of wires, flat band straps or wire rope which has been placed around the package. The lifting hook or hooks are inserted under the package strapping by hand. Each hook is released from the package by remote control, by allowing air pressure to operate an internal latch piston.
Such hooks are commonly suspended in groups from a framework which in turn is lifted by a crane. The suspension means is normally and preferably alloy steel chain. When the hooks are to be attached a load, the suspension framework is set down on top of the load. This results in the hooks lying on the load with the suspension chain for each hook in a relaxed or loose mode.
In this position the suspension chains exibit no directional preference. The hooks may be inserted under the package strapping in either a left to right or right to left motion. However, a suspension chain may be twisted or straight depending on which way the hook is inserted. Once the crane begins lifting and the load is applied to the suspension chains, the chains exhibit a tendency to rotate to a straight, untwisted configuration. If a hook was inserted under the strapping in a direction which causes a twist in the chain, the untwisting tendency of the chain may cause a small safety latch on the hook to be torn off and allow the hook to rotate out from under the strapping causing the load to fall.
This deficiency cannot be overcome by merely putting a swivel in the chain because this allows unrestricted rotation of the hook, permitting the air supply hose to become twisted around the chain. This results in premature failure of the hose due to chafing or rupture due to stretching.
Objects of the present invention are, therefore, to provide an improved swivel-mounted pneumatic-controlled releasing hook device which overcomes the difficulties explained above, to provide such a device in which the hook portion has unrestricted rotational freedom relative to a suspension chain and air supply hose, and to provide a novel means for introducing air pressure under a latch piston which has an upward release movement while allowing both rotational and axial movement of the piston.